Re: A few proposals, this time from the C++ standards committee

[Randy Dunlap <rdunlap@infradead.org>]

On 3/17/24 21:42, Paul E. McKenney wrote:
> On Sun, Mar 17, 2024 at 07:57:31PM -0700, Randy Dunlap wrote:
>>
>>
>> On 3/17/24 19:44, Paul E. McKenney wrote:
>>> On Sun, Mar 17, 2024 at 06:49:17PM -0700, Linus Torvalds wrote:
>>>> On Sun, 17 Mar 2024 at 17:42, Paul E. McKenney <paulmck@kernel.org> wrote:
>>>>>
>>>>> On the other hand, there is much more awareness of concurrency in that
>>>>> group than 20 years ago, so there is hope.
>>>>
>>>> Yeah. But when I say "compiler writers don't understand memory
>>>> ordering", it's not that I think they need to be singled out - pretty
>>>> much *nobody* understands it.
>>>
>>> Fair enough!
>>>
>>>> Christ, I'm supposed to know it fairly well, and I still get it wrong
>>>> myself regularly and have to really think about it (and honestly just
>>>> prefer leaning on a few standard patterns rather than having to think
>>>> about it too much).
>>>>
>>>> So "awareness of concurrency" is one thing, and I agree it's getting
>>>> much better.
>>>>
>>>> Actually getting memory ordering right - even when you are aware of
>>>> concurrency - is another thing entirely.
>>>
>>> Agreed, myself included.  So we should all use the standard patterns where
>>> we can, getting ourselves into memory-model trouble when those patterns
>>> are not cutting it.  And over time, we add to the standard patterns.
>>>
>>> But we are making progress.  Fifty years ago, the consensus was that
>>> developers could not be trusted to get while-loop conditions right.  ;-)
>>
>> I was using for loops and do-until loops 50 years ago, but maybe not "while"
>> loops. Or are you off by 10 years or so?
> 
> So was I.  Yet in the late 1970s, I attended a talk by a guy named
> Edsger Dijktra with examples claiming that you could not trust ordinary
> developers to correctly write "while" loops.  Sort of like some people
> today claim that ordinary developers cannot be trusted to write concurrent
> code.
> 
> Of course, one might reasonably argue that developers cannot be trusted
> to write much of any code at all.  Some days I would agree.  ;-)

Ack that.

-- 
#Randy